The present invention relates to an air outflow valve for use in aircraft applications and, more particularly, to an air outflow valve that incorporates a screw and cable assembly that enhances the reliability of the air outflow valve.
For a given airspeed, an aircraft may consume less fuel at a higher altitude than it does at a lower altitude. In other words, an aircraft may be more efficient in flight at higher altitudes as compared to lower altitudes. Moreover, bad weather and turbulence can sometimes be avoided by flying above such weather or turbulence. Thus, because of these and other potential advantages, many aircraft are designed to fly at relatively high altitudes.
As the altitude of an aircraft increases, the ambient pressure outside of the aircraft decreases and, unless otherwise controlled, air could leak out of the aircraft. Thus, many aircraft are equipped with a cabin pressure control system to maintain and the pressure within the aircraft (so-called xe2x80x9ccabin pressurexe2x80x9d). Also, during flight, variations in aircraft altitude will result in changes in the ambient pressure outside of the aircraft. The cabin control pressure system controls the cabin pressure to within relatively comfortable range and makes gradual changes in the cabin pressure to minimize passenger discomfort. Cabin pressure control systems may be equipped with one or more outflow valves. An outflow valve can assist in controlling cabin pressure by regulating air flow out of the cabin.
One particular type of outflow valve used on C-130 type aircraft has a butterfly plate as the control element to regulate the flow of air out of the cabin. The butterfly plate is connected to a rotationally mounted shaft that causes movement of the butterfly plate. Two control arms are coupled to each side of the shaft. A spring is connected between each of the control arms and the body of the outflow valve and biases the butterfly plate toward the closed position. A pneumatic control diaphragm is also mounted within the outflow valve. Two cable assemblies, one for each arm assembly, mechanically couple the pneumatic control diaphragm to the control arms, via two pulley assemblies. Significantly, a retaining ball is connected to the end of each cable assembly and is inserted into a retaining hole in each arm assembly. The control diaphragm and cable assemblies are positioned and configured such that when the butterfly plate is closed, the cable assembly is under tension. Thus, movement of the pneumatic control diaphragm causes movement of the butterfly plate. While the outflow valve is believed to be generally safe and reliable, under certain circumstances certain drawbacks may exist. One drawback relates to the manual operation of the valve, described in more detail below.
The above-described outflow valve has two general modes of operation, an automatic mode and a manual mode. In the automatic mode, the position of the butterfly plate is controlled by movement of the pneumatic control diaphragm. Specifically, one side of the control diaphragm is exposed to a variable control vacuum, the magnitude of which is modulated by a control system to control the movement of the pneumatic control diaphragm. In the automatic mode, the cable assemblies remain under tension, and as the control diaphragm moves, the cable assemblies cause the control arms, and thus the butterfly plate, to move.
In the manual mode, however, an electric actuator is used instead of using the pneumatic control diaphragm to operate the butterfly plate. Therefore, in the manual mode, the control arms move while the pneumatic control diaphragm does not. This movement results in the cable assemblies no longer being under tension and instead applies a compression force to them, which may cause them to bend and/or kink and to rub against the base of the pulley bracket. This bending, kinking, and rubbing has in some cases caused premature failure of the cable assemblies. As a result, the valves may no longer operate properly in the automatic mode.
In addition to the above-noted drawbacks associated with the cable assemblies and pulley brackets, the control arms may also exhibit certain drawbacks. Specifically, the ball retaining hole in each control arm may inhibit or prevent movement of the retaining ball within retaining hole. This may lead to stress failure at the cable-retaining ball joint. Additionally, the cable assemblies may rub against a roll pin that is positioned in the tops of control arms, or against the edges of the slot that the cables pass through in reaching the ball-retaining hole. This rubbing may increase the likelihood of a stress failure.
Outflow valves of differing designs are available to replace the above-described valve, or the valve could be modified with components that implement a different type of control scheme. These, however, are relatively expensive, time consuming, and potentially complex options.
Hence, there is a need for an outflow valve that overcomes one or more of the above-noted drawbacks. Namely, an outflow valve that does not cause the cable assemblies to bend, kink, or rub when the valve is being operated manually, and/or a valve that exhibits a reduced likelihood for stress failure at the cable-retaining ball joint, and/or a valve that can be modified relatively inexpensively and/or in a relatively non-complex manner. The present invention addresses these needs.
The present invention provides an air outflow valve that is more reliable than the existing air outflow valve, and one or more components to modify existing air outflow valves of this type. The present invention reduces the likelihood that the cable assemblies will bend, kink, or rub when the valve is being operated manually, and/or the likelihood for stress failure at the cable-retaining ball joint. The present invention also provides components that will allow existing air outflow valves to be modified relatively inexpensively and in a relatively non-complex manner.
In one embodiment of the present invention, and by way of example only, an air outflow valve includes a valve body, a valve disk, at least one control arm, at least one biasing element, a control diaphragm, at least one retainer, and at least one cable. The valve disk is movably mounted within the valve body and is moveable through a plurality of positions between a closed position and an open position. Each control arm is coupled to the valve disk. Each biasing element is coupled between each control arm and the valve body for biasing the valve toward the closed position. The control diaphragm is mounted within the valve body. Each retainer is coupled to the control diaphragm and has an opening and an internal surface defining a cavity that extends from the opening a predetermined distance within the retainer. Each cable has a first end coupled to the control arm and a second end inserted through the opening and is slidably retained within the retainer cavity, the second end is moveable within the retainer cavity between the opening and a position along the predetermined distance of the cavity.
In another exemplary embodiment of the invention, a cable assembly for coupling between the diaphragm and a control arm of an air outflow valve includes a retainer and a cable. The retainer has an opening in a first end thereof and an internal surface defining a cavity that extends from the opening a predetermined distance within the retainer. The cable has a first end adapted for coupling to the control arm and a second end that is inserted through the opening and is slidably retained within the retainer cavity, the second end is moveable within the retainer cavity between the opening and a position along the predetermined distance of the cavity.
In still another exemplary embodiment of the invention, a method of modifying an air outflow valve having a valve body, a valve disk movably mounted within the valve body and moveable through a plurality of positions between a closed position and an open position, at least one control arm coupled to the valve disk, at least one biasing element coupled between each control arm and the valve body for biasing the valve disk toward the closed position, a control diaphragm mounted within the valve body, at least one cable assembly having a first end coupled to the control arm and a second end coupled to the control diaphragm, includes the steps of disassembling at least a portion of the valve body and replacing each of the cable assemblies with a replacement cable assembly. Each of the replacement cable assemblies includes a retainer and a cable. The retainer has an opening in a first end thereof and an internal surface defining a cavity that extends from the opening a predetermined distance within the retainer. The cable has a first end adapted for coupling to the control arm and a second end that is inserted through the opening and is slidably retained within the retainer cavity, the second end is moveable within the retainer cavity between the opening and a position along the predetermined distance of the cavity. The disassembled portions of the valve body are then reassembled.
In yet another exemplary embodiment of the invention, a kit for modifying an air outflow valve having a valve body, a valve disk movably mounted within the valve body and moveable through a plurality of positions between a closed position and an open position, and at least one control arm coupled to the valve disk, includes at least one cable assembly having a retainer and a cable. The retainer has an opening in a first end thereof and an internal surface defining a cavity that extends from the opening a predetermined distance within the retainer. The cable has a first end adapted for coupling to the control arm and a second end that is inserted through the opening and is slidably retained within the retainer cavity, the second end is moveable within the retainer cavity between the opening and a position along the predetermined distance of the cavity.
The present invention may also include at least one pulley assembly and at least one control arm that also reduce the likelihood of cable damage. The pulley assembly is mounted within the valve body and includes a rotationally mounted pulley positioned to contact at least a portion of the cable when the cable is in tension. The pulley assembly includes a pulley bracket, at least two support arms, a pulley, and a roll pin. The pulley bracket has a base coupled to the valve body. The support arms extend from the base at a predetermined angle relative to the base, and have a first end coupled to the base and a second end distal to the first end. The pulley is rotationally mounted between the support arms proximate the second ends, and the roll pin is mounted between the support arms proximate the first ends. The control arm includes a main body portion and at least two control arms. The control arms extend from the main body portion substantially parallel with one another and are spaced apart from one another to form a slot there between, and each arm includes an indentation collocated with the indentation in the other arm to form a retaining hole for receiving a retaining ball. The retaining hole is dimensioned so as to allow the retaining ball to move within the retaining hole.
Other independent features and advantages of the preferred outflow valve and cable assembly will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.